If you're in a corporate environment with control over the infrastructure, low DNS TTLs allow you to mostly guarantee a failover. There will always be clients t

If you're in a corporate environment with control over the infrastructure, low DNS TTLs allow you to mostly guarantee a failover. There will always be clients that ignore TTLs, but most of them are fixed by IT rebooting the box. As the poster says, when it comes to the public internet DNS TTLs are more like guidelines. Luckily most client DNS caches are cleared on a reboot. FYI, if I remember correctly Windows (and MacOS?) used to cache negative responses for "a while".